There’s a lot more variety than there used to be with different height options

It depends on if you’re looking at a standard frame that requires a box spring or a platform style bed.

For how much weight the frame can hold once constructed. The ones in-store are often cheaper and less sturdy (really low weight limits) than the ones available online only, unless you’re going to a proper furniture store

Most of the metal beds you can find online also have weight limits included in at least one of the pictures!